Electrical combination lock

ABSTRACT

An electrical combination lock includes a hidden magnetic reed array, a pulse counter coupled by digital circuitry to the reed array, and an electrically controllable lock coupled to the counter. If predetermined reeds of the array are operated with a magnet in a predetermined sequence within a predetermined time, the counter provides a signal which causes the lock to open. If the reeds are operated in any other order, such operation disables the counter for a predetermined unit of time during which the lock cannot be opened. Thus, knowledge of the location of the magnetic reeds and the sequential operation of particular magnetic reeds within a predetermined time are required in order to open the lock.

United States Patent [1 1 Hughes 1 Nov. 13, 1973 ELECTRICAL COMBINATION LOCK Primary Examiner-J. D. Miller Assistant Examiner-Harry E. Moose, Jr. [75] Inventor. David C. Hughes, Cos Cob, Conn. Atwmey Alan R Levine [73] Assignee: Intelligence Services Products Division Inc, Syosset, [57] ABSTRACT [22] Filed: June 1972 An electrical combination lock includes a hidden mag- 211 App], 2 4, 4 netic reed array, a pulse counter coupled by digital circuitry to the reed array, and an electrically controllable lock coupled to the counter. If predetermined [52] [1.8. CI 317/134, 70/278, 70/DIG. 81 reeds of the army are operated with a magnet in a [51] Int. Cl. E05b 49/00 determined sequence hi a predetermined time the [58] Field of Search 317/134; 70/271, counter provides a Signal which causes the lock to 70/273' 1310' 81; 200/43 45 open. If the reeds are operated in any other order,

such operation disables the counter for a predeter- [56] References Cited mined unit of time during which the lock cannot be UNITED STATES AT NTS opened. Thus, knowledge of the location of the mag- 3,641,396 2 1972 Kossen et a] 317/134 netic r s and t s qu tial peration of particular 3,673,466 6/1972 Krueger magnetic reeds within a predetermined time are re- 3,619,728 11/1971 Cooper, Jr 317/134 quired in order to open the lock.

FOREIGN PATENTS 0R APPLICATIONS 10 Claims 3 Drawing Figures 1,474,424 4/1966 France 70/277 w q in V i 9 52 2 K i 0 5,, 5e

N v/o2 2 62$ 25 W5 aaf 44 {D Z 5 44 R L. 66

1: .90 fl V 77 f 75 aaJ I 75 -3 a2 U 54 POM/E su 4y /5 This invention relates to electrical combination locks and in particular to an electrical combination lock wherein particular switches of an array must be sequentially operated within a predetermined time interval in order to open the lock.

It is an object of the present invention to provide an electrical combination lock which cannot be opened for a predetermined period of time after an incorrect code has been applied, thereby hindering the use of experimentation to open the lock.

It is another object of the present invention to provide an electrical combination lock wherein the code for opening the lock is readily changeable.

It is still another object of the present invention to provide an electrical combination lock which is magnetically actuated, thereby enabling concealment of the lock from unauthorized users.

The above objects are met, according to the invention, by an electrical combination lock having (a) a pulse counter; (b) a plurality of switch means; (c) an electrically controllable lock; (d) means for permitting said lock to be opened only when said counter receives a predetermined number of pulses; and (e) means responsive to operation of said switch means in a predetermined sequence for enabling said counter to receive pulses for only a predetermined time period, for providing pulses to said counter, and for opening said lock.

Additional objects and features of this invention will become apparent by reference to the following description in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an electrical combination lock according to the present invention;

FIG. 2 is a perspective view of a wall of an enclosure having an array of magnetically-operable switches within it, the location of said switches being conveyed to authorized'users of the lock by a design on the outer face of the wall, and a magnet in the process of being brought to the design to operate one of the switches; and

FIG. 3 is a cross-sectional view of a portable electromagnet for use in opening the electrical combination lock.

An electrical combination lock according to the invention is schematically illustrated in FIG. 1. In general, the electrical combination lock includes five magnetic reed switches 14-14 which, when operated, activate logic circuits, and a solenoid actuated lock 15 coupled to the logic circuits. Only the movable latch portion 84 of the lock is illustrated. It is to be understood, however, that the latch engages a fixed keeper when the lock is closed and is moved out of engagement with the keeper when the lock is opened. The lock can only be opened if switches 10-12 are operated in a predetermined sequence within a predetermined period of time.

Referring to FIG. 2, to prevent unauthorized users of the combination lock from tampering with its switches 10-14, the switches are fixed in an array to, for example, the hidden face ofa non-magnetic wall 16 of menclosure. The face of the wall 16 is decorated with a design 17, in this example a grid pattern, whose features are used to indicate the location of the switches 10-14 to authorized users. Thus, an authorized user can operate any particular switch with magnetic means 18 whereas an unauthorized user will be burdened with the task of first locating the switches 10-14.

The magnetic means 18 may either be a permanent magnet which is strong enough to close a magnetic reed switch when the magnet is brought into close proximity with such a switch, or an electromagnet, such as is more fully described below.

The logic functions used for opening the lock 15 may be provided using standard components. For example,

the logic functions required by the invention may be provided by using, in conjunction with other standard elements, the following solid state logic components: one RCA CD40l7lA decade counter; one RCA CD4000A NOR gate pair; and one RCA CD4009A six inverter package. In this example of the invention, the foregoing logic components are operated with a 10 volt power supply 34 (FIG. 1) to provide a low level voltage of approximately zero volts and a high level voltage of approximately 10 volts, said voltages, respectively, corresponding to the well-known 0 and 1 binary states.

More specifically, as shown in FIG. 1, the electrical combination lock includes a combination plug 19 having terminals 2l3l. Although the plug 19 is not a necessary part of the invention, the plug is used so as to enable the combination of the lock to be changed by merely changing the connections at the plug 19. For one of a number of possible connections, switch 10 is connected at one end to terminal 22 and at the other end, via wire 33, to the power supply 34. Switch 11 is connected at one end to terminal 21 and at the other end, via wire 33, to the power supply 34. Switch 13'is connected at one end to terminal 24 and at the other end, via wire 33, to the power supply 34. Switch 14 is connected at one end, via wire 33, to the power supply 34, and at the other end to terminal 23 and to terminal 24 via jumper 35. Switch 12 is connected at one end to terminal 25 and at the other end to terminal 26. In the plug 19, each pair of terminals 21 and 27, 22 and 28, 24 and 29, 25 and 30, and 26 and 31, are connected to each other. Thus, terminals 27-31 are available to couple the switches 10-14 to the logic circuits.

The logic circuitry and how it operates to open the lock 15 will now be described. A wire 36 connects terminal 28 to an input of a NOR gate 37, to a grounded resistor 38, and to a grounded capacitor 39. The output terminal of the NOR gate 37 is connected by wire 40 to the reset terminal of a decade counter 41 and to one end of a DC blocking capacitor 42. The other end of the capacitor 42 is connected by wire 43 to an inverter 44, and to a resistor 45 which couples, via wire 51, the power supply 34 to the inverter 44 and the capacitor 42. The output terminal of the inverter 44 is connected by wire 46 to the anode of a diode 47. The cathode of the diode 47 is connected by wire 48 to an input of the NOR-gate 37, to one end of a grounded resistor 49, and to one end of a grounded capacitor 50.

As a result, when the switch 10 is closed momentarily, a positive pulse is applied to the NOR gate 37. If the pulse width exceeds a predetermined value which is determined by the component values of resistor 38 and capacitor 39, the leading edge of the pulse produced by the closing of switch 10 causes the output voltage of the NOR gate 37 to drop to its low voltage state and the output voltage of the inverter 44 to rise to its high voltage state. The low level voltage from the NOR gate 37 enables the decade counter 41, and the high level voltage from the inverter 44 causes the capacitor 50 to charge to a positive voltage which exceeds the threshhold level of the NOR gate 37. The trailing edge of the pulse does not cause the output of the NOR gate 37 to rise to its high voltage state because of the positive voltage on the capacitor 50. However, with time, the capacitor 42 charges and the output voltage of the inverter 44 drops, thereby back-biasing the diode 47. The back-biased diode 47 causes the capacitor 50 to discharge through resistor 49, and when the voltage across the capacitor 50 falls below the threshhold level of the NOR gate 37, the output voltage of the NOR gate 37 rises to its high voltage state. The high voltage state of the output of the NOR gate 37 disables the decade counter 41. Thus, the closure of the switch for a brief period of time enables the decade counter 41 for a period of time determined by the component values of resistors 49, 45 and capacitors 42, 50. Typically, the decade counter 41 is enabled for ten seconds.

Switch 11 is connected by wire 52 to the clock input of the decade counter 41, to a grounded resistor 53, and to a grounded capacitor 54. Thus, each time the switch 11 is closed momentarily, a pulse is applied to the counter 41. If the pulse width exceeds a predetermined value which is determined by the component values of resistor 53 and capacitor 54, and the counter 41 is enabled, as described above, the counter will count the pulse produced each time that the switch 11 is closed.

Each of the output terminals (not shown) of the decade counter 41 is connected to one of the terminals 56-65 of a slide switch 66, and the wiper arm 67 of the slide switch 66 is adjustable to engage any oneof the terminals 56-65. Each of the terminals 56-65 provides a high level output voltage only when a predetermined number of pulses have been applied to the enabled decade counter 41. For example, terminal 60 only provides a high level voltage when 5 input pulses are applied to the decade counter 41 via line 52. Thus, the output voltage on a wire 68 coupled'to the wiper arm 67 is at a high voltage state only when a certain number of pulses have been applied to the counter 41 and the wiper arm 67 is connected to the terminal of the counter whose output voltage is caused to rise by the certain number of pulses. Since the wiper arm 67 may be adjusted to make contact with any one of the terminals 56-65, the use of switch 66 provides another means for changing the combination of the electrical combination lock,

The wire 68 is connected to an inverter 69 whose output is connected to terminal 30. As previously described, terminal 30 is coupled to terminal 31 via switch 12. Terminal 31 is connected by a wire 71 to one end of a resistor 72 and to one end of a resistor 73. The other end of resistor 72 is connected to the base of an NPN transistor 76 and, via resistor 74, to the power supply 34. The other end of resistor 73 is connected tothe base of a PNP transistor 77 and, via resistor 75, to

grounded solenoid 83. The solenoid 83 is used to control the latch 84 of the lock 15, and the diode 82 is used to protect the Darlington circuit from current spikes. With the arrangement described, the resistors 72-75 normally bias the transistors 76, 77 below their cut-off voltages. However, if the switch 12 is closed when a predetermined number of pulses is applied to the enabled decade counter 41, the positive voltage on the wire 68 causes the transistors 76, 80 and 81 to conduct, thereby energizing the solenoid 83 which pivots latch 84 and opens the lock. Upon deenergization of solenoid 83, a spring returns latch 84 to its locked position.

From the foregoing, it may be seen that the electrical combination lock can be opened by closing switch 10, closing switch 11 an appropriate number of times which is determined by the setting of the slide switch 66, and by closing switch 12. However, the switches 10-12 must be operated within the predetermined time ground. The emitter of transistors 77 is grounded and interval. To prevent unauthorized openings of the lock 15, the electrical combination lock also includes a number of traps, the circuitry of which is described below.

A wire 86 connects terminal 29 to an input of a NOR gate 87, to a grounded resistor 88, and to a grounded capacitor 89. The output terminal of the NOR gate 87 is connected to one end of a DC blocking capacitor 91, and via inverter 90 to the clock enable terminal of the decade counter 41. The other end of the blocking capacitor 91 is connected by wire 92 to an inverter 93, and to a resistor 94 which couples the power supply 34 to the inverter 93 and the capacitor 91. The output terminal of the inverter 93 is connected by wire 95 to the anode of a diode 96. The cathode of the diode 96 is connected by wire 97 to an input of the NOR gate 87, to one end of a grounded resistor 98, and to one end of a grounded capacitor 99. As a result, when either switch 13 or 14 is closed momentarily, a positive pulse is applied to the NOR gate 87. If the pulse width exceeds a predetermined value which is determined by the component values of resistor 88 and capacitor 89, the leading edge of the pulse causes the output voltage of the NOR gate 87 to drop to its low voltage state and the output voltages of inverters 93 and 90 to rise to their high voltage state values. This results in disabling the decade counter 41 and causing the capacitor 99 to charge to a positive voltage which exceeds the threshhold voltage level of the NOR gate 87. The trailing edge of the pulse does not cause the output of the NOR gate 87 to rise because of the positive voltage on the capacitor 99. However, with time, the DC blocking capacitor 91 charges and the output of the inverter drops to its low voltage state value, thereby back-biasing the diode 96. The back-biased diode 96 causes the capacitor 99 to discharge through resistor 98, and when the voltage across the capacitor 99 falls below the threshhold level of the NOR gate 87, the output voltage of the NOR gate 87 rises to its normally high voltage state. The high output voltage level at the output of the NOR gate 87 enables the decade counter 41. Thus, the closure of switch 13 or 14 for a brief period of time disables the decade counter 41 for a period of time determined by the component values of resistors 94, 98 and capacitors 91, 99. During the period of time that the decade counter 41 is disabled, it cannot be reset and, therefore, the lock 15 cannot be opened with the procedure described above. Typically, the decade counter 41 is disabled for 20 seconds.

The provide a trap" which prevents the opening of the lock 15 unless switches 10, 11, and 12 are operated a predetermined number of times in the stated order, wire 40 at the output of NOR gate 37 is connected to one end of resistor 101. The other end of resistor 101 is connected to a grounded capacitor 102, and to the input of an inverter 103 whose output is connected to the cathode of a diode 104. The anode of the diode 104 is connected via resistor 105 to wire 36 and to the anode of diode 106. The cathode of diode 106 is connected to the input of NOR gate 87. Before switch is closed, to start a sequence for opening the lock 15, the voltage at the input of the inverter 103 is at a high voltage level, and the voltage at the output of the. inverter 103 is at a low voltage level. Thus, when the switch 10 is closed once, the diode 104 is forward biased and the pulse voltage provided by the momentary closure of switch 10 is dropped across resistor 105. However, the pulse, as previously described, causes the output of the NOR gate 37 to drop, and after a delay provided by resistor 101 and capacitor 102 causes the output of the inverter 103 to rise, thereby back-biasing diode 104. As a result, if after the delay caused by the resistor 101 and capacitor 102, but within the time during which the decade counter 41 is enabled, the switch 10 is closed a second time, the resulting pulse is coupled, via-resistor 105 and diode 106, to an input of NOR gate 87. Thus, the decade counter 41 is disabled for a predetermined period of time, as previously described with respect to a pulse provided by switch 13 or 14. Accordingly, switch 10 cannot be closed more than once if the lock is to be opened.

Further, wire 52, connecting switch 11 to decade counter 41, is connected to one end of a resistor 108, and the other end of resistor 108 is connected to the anode of diode 109 and the anode of diode 110. The cathode of diode 109 is connected to wire 40 and the cathode of diode 110 is connected, via wire 111, to an input of the NOR gate 87. If the switch 10 has enabled the decade counter 41, wire 40 is at a low voltage level, and positive pulses on wire 52 cause the forward biased diode 109 to conduct. Accordingly, the pulse voltage is dropped across resistor 108. However, if the decade counter 41 is not enabled when switch 11 is closed, a

high voltage is applied to the cathode of diode 109 by g the NOR gate 37 and an input pulse supplied byv the switch 11 is coupled via resistor 108, diode 110, and wire 111, to the input of the NOR gate 87, thereby disabling the decade counter 41, in the manner described above, for a predetermined period of time.

As previously described, when'the decade counter 41 is disabled or the wiper arm 67 of switch 66 is connected to a terminal which is at a low voltage state because an incorrect number of pulses have been applied, a low voltage is present on line 68. Therefore, if switch 12 is closed, the transistor 77 is caused, via resistor 113, to conduct. The collector of transistor 77 is connected to the inverter 78 and the output of the inverter 78 is connected to the anode of diode 115. The cathode of diode 115 is connected, via wire 111, to an input of the NOR gate 87. Thus, a premature closure of the switch 12 causes the collector voltage to drop momentarily, and a positive pulse is applied to the NOR gate 87, thereby disabling the decade counter for a predetermined period of time.

From the foregoing it may be seen that the lock 15 can only be opened if the switch 10 is closed once, if

thereafter the switch 11 is closed a predetermined number of times, if the switch 12 is closed after switch 11 has been closed a predetermined number of times, and if switches 10, 11, and 12 are operated as just described, within a predetermined time interval. Any deviation from the sequence set forth above causes the combination lock to be disabled for a predetermined interval of time during which not even the proper sequence will open the lock. I

Since the required closing of the switches l0, l1, and 12 require that a magnet be brought near the switches a predetermined number of times, it is conceivable that one watching the opening of the lock will detect and count the gross movements of the user's hand and arm in the process of opening the lock, thereby obtaining knowledge of the number of pulses required to open the lock. Accordingly, for additional security, the lock may be opened with a portable electromagnet which can be controlled with the less obvious. action of, for example, a finger. Such an electromagnet is disclosed below.

Referring To FIG. 3, a portable electromagnet includes a non-magnetic circular container 117 having a cover 118 through which an actuator 119 extends. In the bottom of the container 117, there is fixed a magnetic member 120 about which there is located a spirally wound wire 12]. One end of wire 121 is connected to an L-shaped metallic contact 122 which is fixed to the wall of the container 1 l7, and the other end of the wire 121 is connected to the top surface of an annular abutment 123 extending from the inside wall of the container 117. The abutment 123 and an arcuate member 124 extending from the cover into the circular container 117 serve to secure'a-circular battery 125 in the container, and causes engagement between the case of the battery 125 and wire 121. A portion of the L-shaped metallic contact 122 extends in cantilever fashion over the terminal of the battery 125 and abuts against the base of the actuator 119, thereby biasing a flange 126 on the actuator 119 against the bottom of the cover 118. As a result of this arrangement, when the actuator 119 is depressed, the metal contact engages the terminal of the battery 125 and current flows through the wire 121. The flow of current through wire 121 causes the magnetic member 120-to provide a magnetic field which is useful for operating the magnetic. reed switches. When the actuator 119 is released, the metallic contact 122 springs to its normal position, thereby opening the circuit, returning the actuator to its initial position, and terminating the magnetic field.

With an electromagnet as described, an operator of the electrical combination lock can deceptively approach magnetic switches 10-14 of the array any number of times before actuating the electromagnet with the slight movement of a finger, thereby concealing the number of pulses required to open the lock 15.

In view of all of the above, it should be noted that the electrical combination lock described as an example features a code which can be changed readily by chang- What is claimed is:

1. An electrical combination lock, comprising:

a. a pulse counter having a plurality of outputs;

b. a plurality of switch means;

0. an electrically controllable lock;

d. means for permitting said lock to be opened only when said counter receives a predetermined number of pulses, said means including means for open circuiting all but one of the outputs of said pulse counter and for coupling the one output to one of the switch means; and

e. means responsive to operations of said switch means in a predetermined sequence for enabling said counter to receive pulses for only a predetermined time period, for providing pulses to said counter, and for opening said lock.

2. An electrical combination lock as defined in claim 1 wherein the plurality of switch means includes a hidden array of switches, and including means for actuating any of the hidden switches.

3. An electrical combination lock as defined in claim 2 wherein the plurality of hidden switches include at least one magnetic reed switch, and said actuating means includes magnetic means for operating magnetic reed switches.

4. An electrical combination lock as defined in claim 3 wherein said magnetic means include an electromagnet.

5. An electrical combination lock as defined in claim I wherein said means (e) includes: means responsive to the operation of one of the switch means for enabling the counter for the predetermined period of time, and means responsive to the operation of another of the switch means for providing the pulses to the counter.

6. An electrical combination lock as defined in claim 1 wherein said means (e) includes: means responsive to the operation of another one of the switch means for providing the pulses to the counter, and means responsive to operation of said one of the switch means for opening the lock when the counter has received the predetermined number of pulses.

7. An electrical combination lock as defined in Claim 1 wherein the plurality of switch means further includes first and second switch means; wherein said means (e) includes: means responsive to the operation of the first switch means for enabling the counter for the predeterminedperiod of time, means responsive to the operation of the second switch means for providing the pulses to the counter, and means responsive to operation of said one of the switch means for opening the lock when the counter has received the predetermined number of pulses.

8. An electrical combination lock as defined in claim 7 further including means for keeping the lock closed unless the first, second, and said one switch means are sequentially operated in a predetermined order within the predetermined time period.

9. An electrical combination lock as defined in claim 8 wherein said means for keeping the lock closed includes means responsive to the operation of any of said plurality of switch means in other than said predetermined sequence, for disabling the counter for a predetermined interval of time.

10. An electrical combination lock as defined in claim 1 including means responsive to non-sequential operation of said switch means for disabling said pulse counter for a predetermined period of time. 

1. An electrical combination lock, comprising: a. a pulse counter having a plurality of outputs; b. a plurality of switch means; c. an electrically controllable lock; d. means for permitting said lock to be opened only when said counter receives a predetermined number of pulses, said means including means for open circuiting all but one of the outputs of said pulse counter and for coupling the one output to one of the switch means; and e. means responsive to operations of said switch means in a predetermined sequence for enabling said counter to receive pulses for only a predetermined time period, for providing pulses to said counter, and for opening said lock.
 2. An electrical combination lock as defined in claim 1 wherein the plurality of switch means includes a hidden array of switches, and including means for actuating any of the hidden switches.
 3. An electrical combination lock as defined in claim 2 wherein the plurality of hidden switches include at least one magnetic reed switch, and said actuating means includes magnetic means for operating magnetic reed switches.
 4. An electrical combination lock as defined in claim 3 wherein said magnetic means include an electromagnet.
 5. An electrical combination lock as defined in claim 1 wherein said means (e) includes: means responsive to the operation of one of the switch means for enabling the counter for the predetermined period of time, and means responsive to the operation of another of the switch means for providing the pulses to the counter.
 6. An electrical combination lock as definEd in claim 1 wherein said means (e) includes: means responsive to the operation of another one of the switch means for providing the pulses to the counter, and means responsive to operation of said one of the switch means for opening the lock when the counter has received the predetermined number of pulses.
 7. An electrical combination lock as defined in Claim 1 wherein the plurality of switch means further includes first and second switch means; wherein said means (e) includes: means responsive to the operation of the first switch means for enabling the counter for the pre-determined period of time, means responsive to the operation of the second switch means for providing the pulses to the counter, and means responsive to operation of said one of the switch means for opening the lock when the counter has received the predetermined number of pulses.
 8. An electrical combination lock as defined in claim 7 further including means for keeping the lock closed unless the first, second, and said one switch means are sequentially operated in a predetermined order within the predetermined time period.
 9. An electrical combination lock as defined in claim 8 wherein said means for keeping the lock closed includes means responsive to the operation of any of said plurality of switch means in other than said predetermined sequence, for disabling the counter for a predetermined interval of time.
 10. An electrical combination lock as defined in claim 1 including means responsive to non-sequential operation of said switch means for disabling said pulse counter for a predetermined period of time. 